“Whenever [President Obama] can’t get what he wants — because, quite frankly, the American people have rejected his agenda — now this president wants to act as if he’s a king, as if he’s a dictator,” said New Jersey Gov. ... more >

Gun control surged to the forefront of the 2016 campaign Sunday as Republicans unloaded on President Obama’s anticipated executive orders on background checks, taking advantage of a potent wedge issue less than a month before the Iowa caucus.

Republican presidential hopefuls didn’t hold back in Sunday appearances: Carly Fiorina described the president’s repeated use of executive orders as “lawless,” while Jeb Bush called it “dangerous.” Several candidates vowed to overturn any unilateral action on firearms access with executive orders of their own if elected.

“The president is a petulant child,” New Jersey Gov. Chris Christie told “Fox News Sunday.” “Whenever he can’t get what he wants — because, quite frankly, the American people have rejected his agenda now this president wants to act as if he’s a king, as if he’s a dictator.”

Businessman Donald Trump promised to rescind any number of Obama executive orders, adding, “I don’t like anything having to do with changing our Second Amendment.”

“The one thing good about executive orders: The new president, if he comes in — boom, first day, first hour, first minute, you can rescind that,” Mr. Trump told “Face the Nation” on CBS.

Mr. Obama is slated to meet Monday with Attorney General Loretta E. Lynch to finalize the details of executive orders expanding background checks, a decision he deems necessary given that Congress has done “nothing” in the aftermath of recent mass shootings.

“We know we can’t stop every act of violence. But what if we tried to stop even one?” Mr. Obama said Friday during his weekly address. “What if Congress did something, anything, to protect our kids from gun violence?”

His final-year push is seen as a last-ditch attempt to carve a legacy on firearms restrictions after a year that saw a half-dozen high-profile shootings, culminating in the Dec. 2 attack in San Bernardino, California, by Islamist radicals who gunned down 14 people before they were killed in a police shootout.

Mr. Obama’s cause is expected to receive a boost from a one-hour CNN special airing Thursday, “Guns in America,” featuring a live town hall meeting with the president at George Mason University in Fairfax, Virginia.

On the Democratic side, Vermont Sen. Bernard Sanders said Sunday he would prefer to see Mr. Obama work with Congress to enact background checks legislation. The executive order is expected to focus on requiring small-scale or part-time firearms dealers to obtain licenses and conduct background checks on buyers.

“I would prefer that we could have bipartisan support, but the truth is Republicans are not interested in doing anything about gun safety,” Mr. Sanders said on CNN’s “State of the Union.” “I think the vast majority of the American people are horrified by the mass shootings that we have seen [and] they want action.”

Mr. Sanders, a candidate for the Democratic presidential nomination, has in the past shown less enthusiasm than most liberals for gun control measures as an independent who represents a pro-Second Amendment state.

“Obviously, bipartisan activity in the Congress would be preferable, but I think the president is doing what the American people would like him to do,” Mr. Sanders said.

Clearly, however, Republicans see gun rights as a winning issue, as does the National Rifle Association, which released an online ad Sunday mocking Democratic front-runner Hillary Clinton’s support for restrictions on firearms.

Republican candidates focused Sunday on Mr. Obama’s use of executive orders rather than the content of the executive orders, which has not yet been released.

“His first impulse is always to take rights away from law-abiding citizens, and it’s wrong,” Mr. Bush said on “Fox News Sunday.” “And to use executive powers he doesn’t have is a pattern that is quite dangerous. It’s not a surprise that people don’t believe that our government is working on their behalf anymore when you have a president that recklessly uses executive authority that the Constitution doesn’t provide him.”

Mrs. Fiorina, the former Hewlett-Packard CEO, called Mr. Obama “lawless in his use of executive orders, whether those orders are around immigration or whether those executive orders are around gun control.”

Sales of firearms surged after the San Bernardino shooting and the previous terrorist attack on Paris as fears over the spread of terrorism into the West increased.

“It is delusional, dangerous, not to mention unconstitutional, for Barack Obama and Hillary Clinton to continue to talk about climate change and gun control in the wake of a Paris terrorist attack, a San Bernardino terrorist attack, instead of talking about how they plan to defeat ISIS,” she said on CNN’s “State of the Union,” using an acronym for the Islamic State terror group.

She said many of those who violate gun control laws now on the books go unprosecuted, such as Dylann Roof, the suspect in the June 17 church shooting in Charleston, South Carolina.

“That is why you get a situation like, say, Chicago, where you have very tight gun control laws and incredible levels of gun violence, and how you get a situation like South Carolina, where someone who never should have been permitted to purchase a gun got to purchase a gun because somehow they got through the cracks,” Mrs. Fiorina said. “Let’s enforce the laws that we have.”

Mr. Christie predicted any such executive order would be rejected by the courts while defending his own record on firearms. In 2013 the NRA gave him a grade of “C” after he signed 10 gun-related bills as governor.

One of those bills banned the sale of guns to those on the terror watch list. As president, he said, “I would make sure that terror watch list was actually accurate.”

“I think most Americans believe if you’re on the terror watch list, you shouldn’t be able to buy guns,” Mr. Christie said. “But I also have vetoed the 50-caliber rifle ban. I’ve also vetoed a statewide ID system. I’ve also vetoed a reduction in the magazine ban, and I’ve also pardoned six different folks so far who have been caught up very unfairly, in my view, in New Jersey’s gun laws.”